KR102077317B1 - Optical film and display device comprising the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical film exhibiting excellent glossiness and reflectance, and excellent optical properties such as an appropriate level of haze properties, and an image display device including the same. The optical film is a light transmissive base film; An antiglare layer comprising a binder containing a (meth) acrylate-based crosslinked polymer, organic microparticles having a micron scale dispersed on the binder, and nanoparticles having a nanoscale inorganic dispersion dispersed on the binder; And a low refractive layer formed on the antiglare layer and comprising a binder resin containing a (co) polymer of a photopolymerizable compound and hollow silica particles dispersed in the binder resin. It indicates a predetermined particle size distribution, refractive index difference and content range.

Description

Optical film and image display device including the same {OPTICAL FILM AND DISPLAY DEVICE COMPRISING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical film exhibiting excellent glossiness and reflectance, and excellent optical properties such as an appropriate level of haze properties, and an image display device including the same.

In an image display device such as an organic electroluminescent element (OELD) or a liquid crystal display element (LCD), it is required to prevent a decrease in contrast and a decrease in visibility due to reflection or reflection of external light. For this purpose, an optical laminated film such as an antireflection film is formed on the surface of an image display device in order to reduce light reflection, reflection, or the like by scattering light or optical interference.

For example, in a liquid crystal display element etc., the optical laminated film containing an anti-glare layer has been generally formed before. The anti-glare layer mainly includes a binder and fine particles contained in the binder, and these fine particles are usually formed so that a part thereof protrudes from the surface of the binder. That is, the anti-glare layer can suppress the visibility deterioration of the image display device by controlling the light scattering / light reflection of the fine particles protruding from the binder surface.

However, in the case of the previously known anti-glare layer and optical film, the glossiness of the surface is often high, and in many cases, reflection of external light is still difficult to be suppressed, which is enough to sufficiently reduce the contrast and visibility of the image display device. Could not be suppressed. Moreover, in the previous anti-glare layer and the optical film, proper control of surface irregularities was difficult, so that the glare defects due to irregular irregularities often appeared, and scattering or reflection of external light, etc. could not be properly controlled. This also became one factor of lowering optical characteristics such as haze characteristics or glossiness of the optical film.

As a result, the existing anti-glare layer and the optical film are not enough optical properties, such as haze characteristics, reflectance or glossiness, there is a disadvantage that does not sufficiently improve the contrast / visibility of the image display device, which is due to the optical properties of the optical film Further improvements are constantly being requested.

Accordingly, the present invention provides an optical film exhibiting excellent glossiness and reflectance, and excellent optical properties such as appropriate haze properties.

This invention also provides the image display apparatus containing the said optical film.

The present invention is a light-transmissive base film;

An antiglare layer comprising a binder including a (meth) acrylate-based crosslinked polymer, organic microparticles having a micron scale dispersed on the binder, and nanoparticles having a nanoscale inorganic dispersion dispersed on the binder; And

A low refractive layer formed on the antiglare layer and including a binder resin containing a (co) polymer of a photopolymerizable compound and hollow silica particles dispersed in the binder resin; Including,

When the total average particle diameter of the organic and inorganic fine particles is D average, and the organic and inorganic fine particles are arranged in descending order from the smallest particle size, the particle size of the fine particles corresponding to the cumulative size of 25% corresponds to D25, and the cumulative 75% of the number. When the particle diameter of the fine particles to be defined is D75, the (D75-D25) / D average is 0.25 or less,

The absolute value of the difference in refractive index between the organic and inorganic fine particles and the binder is 0.01 to 0.25,

The total content of the organic and inorganic fine particles is 1 to 30% by weight of the total content of the antiglare layer,

An optical film having a 60 ° glossiness deviation value of 3% to 10% and a total haze of 1 to 5%.

In addition, the present invention is a light-transmitting base film;

An antiglare layer comprising a binder containing a (meth) acrylate-based crosslinked polymer and a plurality of light-transmitting fine particles of a sub-micron scale dispersed on the binder; And

A low refractive layer formed on the antiglare layer and including a binder resin containing a (co) polymer of a photopolymerizable compound and hollow silica particles dispersed in the binder resin; Including,

When the total average particle diameter of the light-transmitting fine particles is D average, and the light-transmitting fine particles are arranged in descending order from the smallest particle size, the particle size of 25% cumulative particles is D25, and the particle size of 75% cumulative particles When is defined as D75, the (D75-D25) / D average is 0.04 to 0.15,

The absolute value of the difference in refractive index between the light transmitting fine particles and the binder is 0.02 to 0.25,

The total content of the light transmitting fine particles is 1 to 30% by weight of the total content of the antiglare layer,

Reflectance is 0.5% to 2.5%,

An optical film having a 60 ° glossiness deviation value of 3 to 10% and a total haze of 1 to 5%.

This invention also provides the image display apparatus containing the said optical film.

Hereinafter, an optical film and an image display device including the same according to exemplary embodiments of the present invention will be described.

As used herein, micron (μm) scale refers to having a particle size or particle size of less than 1 mm, ie less than 1000 μm, and nano (nm) scale refers to less than 1 μm, ie less than 1000 nm Refers to having a particle size or particle diameter, and sub-micron scale refers to having a particle size or particle size of the micron scale or the nano scale.

In addition, a photopolymerizable compound collectively refers to a compound which causes crosslinking, curing or polymerization reaction when light is irradiated, for example, visible light or ultraviolet light.

In addition, (meth) acryl [(meth) acryl] is meant to include both acryl and methacryl.

In addition, (co) polymer is meant to include both co-polymers and homo-polymers.

In addition, silica hollow particles are silica particles derived from a silicon compound or an organosilicon compound, and mean particles having a void space on the surface and / or inside of the silica particles.

According to one embodiment of the invention, a transparent substrate film;

An antiglare layer comprising a binder containing a (meth) acrylate-based crosslinked polymer, organic microparticles having a micron scale dispersed on the binder, and nanoparticles having a nanoscale inorganic dispersion dispersed on the binder; And

A low refractive layer formed on the antiglare layer and including a binder resin containing a (co) polymer of a photopolymerizable compound and hollow silica particles dispersed in the binder resin; Including,

When the total average particle diameter of the organic and inorganic fine particles is D average, and the organic and inorganic fine particles are arranged in descending order from the smallest particle size, the particle size of the fine particles corresponding to the cumulative size of 25% corresponds to D25, and the cumulative 75% of the number. When the particle diameter of the fine particles to be defined is D75, the (D75-D25) / D average is 0.25 or less,

The absolute value of the difference in refractive index between the organic and inorganic fine particles and the binder is 0.01 to 0.25,

The total content of the organic and inorganic fine particles is 1 to 30% by weight of the total content of the antiglare layer,

An optical film having a 60 ° glossiness deviation value of 3% to 10% is provided.

According to the results of continuous experiments of the present inventors, in the antiglare layer including the organic and inorganic fine particles dispersed in the (meth) acrylate-based binder, by controlling the particle size distribution of the organic and inorganic fine particles to an appropriate level, the (D75-D25) It is possible to provide an anti-glare layer and an optical film having excellent anti-glare properties by controlling the value of the / D average is 0.25 or less, or 0.04 to 0.15, and controlling the binder composition and the difference in refractive index of the binder and the fine particles. Confirmed.

Since the particle size in the antiglare layer may be uniform through the particle size distribution control, the size of the unevenness protruding to the surface of the antiglare layer is uniformly and appropriately controlled to adjust the haze characteristics and glossiness of the antiglare layer to a desirable range. Seems to be. In addition, by controlling the difference between the refractive index of the binder and the fine particles, it is possible to effectively suppress scattering or reflection of external light, thereby providing an antiglare layer and an optical film having excellent antiglare characteristics and optical characteristics. If the particle size distribution range is out of the above-described range or out of the refractive index difference, variation in haze characteristics of the optical film may be severe, or glossiness may be increased, and thus optical characteristics / antiglare characteristics may be greatly reduced.

In addition, in the optical film of one embodiment, the total content of the organic and inorganic fine particles included in the antiglare layer is, for example, 1 to 30% by weight, or 2 to 20% by weight, or 3 to 10% by weight, or 3 To an appropriate level of from 5% by weight. As a result, it was confirmed that the optical properties / anti-glare properties of the optical film can be further improved. If the total content of the fine particles is too small, the surface irregularities on the antiglare layer may not be properly implemented, so scattering / reflection of external light may not be properly controlled, and thus antiglare characteristics may be greatly reduced. On the contrary, if the total content of the fine particles is too large, the refraction of the transmitted image light may increase to significantly reduce the image sharpness of the optical film.

In addition, the optical film of the embodiment includes a specific binder composition described below, and specifically, a binder may be formed using a compound having 3 to 6 functionalities and a compound having 10 or more functionalities. As a result, the optical properties of the binder can be optimized, and at the same time, the difference in refractive index with the above-described fine particles can be properly controlled to optimize the optical properties / anti-glare properties such as haze properties or glossiness of the optical film.

In addition, the optical film of the embodiment further includes a hollow silica particle-containing low refractive layer formed on the antiglare layer. By the formation of such a low refractive layer, the external light reflection of the optical film can be further suppressed, whereby the optical properties of the optical film can be further improved.

As such, the optical film of one embodiment optimizes the configuration of the antiglare layer and forms a low refractive index layer, thereby providing excellent optical and antiglare characteristics such as low glossiness, glossiness variation and reflectance, and an appropriate level of haze characteristics. Can be represented.

Hereinafter, the optical film of one embodiment will be described in detail for each element.

The optical film of the embodiment includes a light-transmitting base film exhibiting at least light transmittance to visible light, as a representative example cellulose ester base film, polyester base film, poly (meth) acrylate base film or polycarbonate It may include a base substrate film. More specific examples of such a transparent base film, for example, triacetyl cellulose (TAC) film, polyethylene terephthalate (PET) base film, polyethylene naphthalate (PEN) base film, polyacrylate (PA) The base film, the polycarbonate (PC) base film, or the polymethacrylate (PMMA) base film and the like, and the like, as well as any resin film known to be applicable as the base film of the optical film may be used. .

In addition, in consideration of the excellent mechanical properties of the base film, water resistance, and the excellent optical properties of the optical film of one embodiment, the light-transmitting base film is 20 to 500㎛, or 30 to 200㎛, or 40 to 150㎛ It can be a film having a thickness of.

In addition, the optical film of one embodiment includes an antiglare layer formed on the base film. As described above, by controlling the refractive index and the binder refractive index difference, the particle size distribution and the content range of the fine particles contained in the anti-glare layer, it is possible to greatly improve the anti-glare characteristics and optical properties of the anti-glare layer and the optical film, etc. have.

In such an antiglare layer, the binder may be a crosslinked (co) polymer of a polyfunctional (meth) acrylate-based compound having a trifunctional or higher (meth) acrylate-based functional group. In a more specific example, as the multifunctional (meth) acrylate-based compound having a trifunctional or higher (meth) acrylate group, a (meth) acrylate compound and / or 10 or more functional groups of 3 to 6 functional monomolecular forms Polyurethane-based polymers having a (meth) acrylate-based functional group, poly (meth) acrylic-based polymers or polyester-based polymers may be used together.

By the composition of such a binder, the difference in refractive index of the binder and the refractive index with the fine particles can be controlled to a more appropriate level. Moreover, it can contribute to maintaining the haze characteristic of the said glare-proof layer and an optical film at an appropriate level, and to improve image sharpness further. If only 3 to 6 functional monomolecular (meth) acrylate-based compounds are used, the haze characteristics may be out of an appropriate range, or the image sharpness may be lowered, and further, the optical characteristics of the antiglare layer may be lowered. This makes it difficult to achieve low glossiness and its deviation value.

Specific examples of the (meth) acrylate-based compound of the 3-6 functional monomolecular form include a compound of the monomolecular form having a (meth) acrylate-based functional group having a molecular weight of 3-6 and an aromatic ring (for example, UA-306T and the like used in the following examples), pentaerythritol tri (meth) acrylate or trialkylolpropane tri (meth) acrylate and the like.

And as a polyurethane-type polymer, a poly (meth) acrylic-type polymer, or polyester-type polymer which has the said (functional) acrylate-type functional group or more, the main chain of a polyurethane type polymer, a poly (meth) acrylic type polymer, or a polyester type polymer Polymers having an average of 10 to 80, or an average of 10 to 50 (meth) acrylate-based functional groups bonded thereto may be used, and such polymers may have a weight average molecular weight of 1000 to 200000.

In addition, the (meth) acrylate type compound of the said 3-6 functional monomolecular form, and the polymer which has the said (10) functional or more (meth) acrylate type functional group are a weight ratio of 1: 1: 1-10: 1, for example. Or in a weight ratio of 2: 1 to 5: 1.

By using the above-described composition to obtain a binder in the form of a crosslinked (co) polymer, the refractive index of the binder is controlled in an appropriate range of, for example, 1.50 to 1.60, or 1.50 to 1.54, or 1.51 to 1.53, to the antiglare layer. It is possible to more effectively adjust the appropriate refractive index difference with the fine particles included, and further improve the haze characteristics, image sharpness, glossiness, and variation of the antiglare layer and the optical film.

In the anti-glare layer, on the other hand, a plurality of light-transmitting fine particles having a sub-micron scale dispersed on a binder, for example, organic fine particles having a micron scale, and nano (nm) scale Inorganic fine particles of the polymer. Such light-transmitting fine particles have a refractive index such that the absolute value of the refractive index difference from the binder described above is 0.01 to 0.25, or 0.02 to 0.25, or 0.02 to 0.10, so that the antiglare layer has low glossiness, appropriate haze characteristics, and excellent antiglare characteristics. Can be represented.

As the organic fine particles, all of the resin particles previously known to be usable in the antiglare layer and the like can be used without particular limitation, and specific examples thereof include polystyrene resin, poly (meth) acrylate resin or poly (meth) acrylate. The resin fine particle containing -co-styrene-type copolymer resin is mentioned.

In addition, such organic fine particles may be, for example, spherical particles having a particle diameter of 1 to 5 µm or 1.5 to 4 µm and having a refractive index of 1.5 to 1.57, or 1.51 to 1.56, or 1.53 to 1.56. .

As the inorganic fine particles, metal oxide fine particles containing silica, alumina, zirconia, or titania may be used. For example, as spherical particles having a particle diameter of 10 nm to 300 nm or 50 to 200 nm, 1.4 to 1.75, or , 1.4 to 1.65, or 1.42 to 1.48, or 1.42 to 1.45.

The light-transmitting fine particles including the organic / inorganic fine particles described above may have a uniform particle size distribution as described above, and thus, the size of the unevenness protruding to the surface of the anti-glare layer is uniformly and appropriately controlled so that The haze property or glossiness can be adjusted to a preferred range, and as a result, the antiglare layer and the optical film of one embodiment can exhibit excellent antiglare properties / optical properties.

More specifically, the D average of the light-transmitting fine particles may be 1.7㎛ to 2.3㎛, or 1.8㎛ to 2.2㎛, D25 may be 1.5㎛ to 2.1㎛, or 1.8㎛ to 2.0㎛, D75 is 1.9 micrometers to 2.5 micrometers, or 1.9 micrometers to 2.2 micrometers. As a result, the value of the (D75-D25) / D average is controlled to 0.25 or less, or 0.04 to 0.15, so that the optical film of one embodiment may exhibit excellent optical properties.

In addition, the plurality of light-transmitting fine particles, for example, the organic and inorganic fine particles described above, have a total content thereof, for example, 1 to 30% by weight, or 2 to 20% by weight, based on the total content of the antiglare layer. %, Or 3 to 10% by weight, or 3 to 5% by weight can be controlled to an appropriate level. The organic fine particles and the inorganic fine particles may be used in a weight ratio of 4: 1 to 1: 2. As already described above, the content of each of the light transmitting fine particles is adjusted to an appropriate range, the optical film of one embodiment may exhibit more excellent optical properties and the like. If the content range of the fine particles is outside the appropriate range, the surface irregularities on the anti-glare layer is not properly implemented, so that scattering / reflection of external light is not properly controlled, the anti-glare property is deteriorated, or the refraction of the light is increased, resulting in an image of the optical film. Sharpness can be greatly degraded.

In addition, the anti-glare layer may have a thickness of 1 to 10 μm, or 2 to 8 μm, and each of the above-described fine particles may be dispersed in the anti-glare layer or may suppress reflection or scattering of external light while at least a part thereof protrudes. have.

The anti-glare layer formed to have the composition and thickness described above, and the particle size distribution of the light-transmitting fine particles can have excellent anti-glare properties by appropriately suppressing scattering or reflection of external light, and excellent in low gloss and reflectance, and suitable haze properties. Optical properties can be exhibited. The excellent optical properties of such an antiglare layer may be defined by low glossiness / reflectivity of the surface, haze characteristics, and the like. For example, the antiglare layer and the optical film may have a reflectance of 0.5% to 2.5%, or 0.7% to 2.0%, and 60 ° glossiness of 45% to 70%, or 50% to 65%, or 50 % To 60%, the 60 ° glossiness is measured 10 times and the 60 ° glossiness deviation value calculated by the formula [(maximum measured value-minimum measured value) / average value] is 3% to 10% Or 3% to 8%, or 5% to 8%.

In addition, the antiglare layer and the optical film may maintain an appropriate level as the total haze is 1 to 5%, or 2 to 4%, or 2.5 to 3.5%. When the total haze is too high, it is obvious that the optical properties are deteriorated, and even when the total haze value is too low, the external reflection image is not scattered and viewed, so that the visibility and image sharpness of the screen may be deteriorated.

On the other hand, the anti-glare layer may be formed by a composition including a photopolymerizable compound, a photoinitiator, and an organic solvent including a (meth) acrylate-based compound having a composition as described above.

In such compositions, conventionally known photoinitiators can be used as the photoinitiator without great limitation. Examples of the photoinitiator are selected from 1-hydroxycyclohexylphenyl ketone, benzyl dimethyl ketal, hydroxydimethylacetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin butyl ether. One single substance or a mixture of two or more thereof.

In this case, the photoinitiator may be added in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the photopolymerizable compound of the (meth) acrylate compound. When the photoinitiator is included in less than 0.1 parts by weight based on 100 parts by weight of the photopolymerizable compound, sufficient photocuring may not occur due to ultraviolet irradiation, and when included in excess of 10 parts by weight based on 100 parts by weight of the photopolymerizable compound. The adhesion of the antiglare layer and the base film may be reduced. Furthermore, when the photoinitiator is included in an excessively large content, the anti-glare layer and the optical film including the same may be yellowed by an unreacted initiator over time, thereby deteriorating optical characteristics of the optical film.

In addition, the composition may further include an organic solvent. When such an organic solvent is added, the constitution is not limited, but in consideration of securing the proper viscosity of the composition and the film strength of the film to be finally formed, it is preferably 50 to 700 parts by weight based on 100 parts by weight of the photopolymerizable compound. By weight, more preferably 100 to 500 parts by weight, most preferably 150 to 450 parts by weight can be used.

At this time, the type of organic solvent that can be used is not limited in its configuration, but lower alcohols, acetates, ketones, cellosolves, dimethylformamide, tetrahydrofuran, propylene glycol monomethyl ether, toluene One or more mixtures selected from the group consisting of xylenes can be used.

In this case, the lower alcohols include methanol, ethanol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, diacetone alcohol and the like. The acetates may be methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, or cellosolve acetate, and the ketones may be methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, or acetone. have.

Meanwhile, the antiglare layer forming composition may further include at least one additive selected from the group consisting of a dispersant, a leveling agent, a wetting agent, an antifoaming agent, and an antistatic agent. In this case, the additive may be added in the range of 0.01 to 10 parts by weight based on 100 parts by weight of the photopolymerizable compound, respectively.

The anti-glare layer may be formed by applying the above-described composition to one surface of the light-transmissive base film and proceeding with drying and photocuring. Such drying and photocuring conditions may be in accordance with general process conditions for forming an anti-glare layer. Process conditions are also described in the examples below.

On the other hand, the optical film of the above-described embodiment further includes a low refractive layer formed on the anti-glare layer. The low refractive index layer may include a binder resin containing a (co) polymer of a photopolymerizable compound and hollow silica particles dispersed in the binder resin.

By including such a low refractive index layer, the reflection itself in the light transmissive base film can be reduced, and as a result, the generation and reflectance of the interference fringe in the optical film of one embodiment can be further reduced. In addition, by using such a low refractive index layer, it is possible to reduce the diffuse reflection on the display surface of the image display device to further improve the resolution and visibility.

The low refractive index layer may have a refractive index of 1.3 to 1.5, and may have a thickness of 1 to 300 nm, for example, to effectively suppress reflection in the base film, diffuse reflection on a display surface of a display device, and the like.

Meanwhile, the low refractive index layer may be formed from a photocurable coating composition for forming a low refractive index layer including a photopolymerizable compound and hollow silica particles. In detail, the low refractive layer may include a binder resin including a (co) polymer of a photopolymerizable compound and hollow silica particles dispersed in the binder resin.

The photopolymerizable compound included in the low refractive layer may include a monomer or oligomer including a (meth) acrylate or a vinyl group. Specifically, the photopolymerizable compound may include a monomer or oligomer containing (meth) acrylate or vinyl group of one or more, two or more, or three or more.

Specific examples of the monomer or oligomer containing the (meth) acrylate include pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate and dipentaerythritol hexa (meth). ) Acrylate, tripentaerythritol hepta (meth) acrylate, triylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, trimethylolpropane tri (meth) acrylate, trimethylolpropane polyethoxy tri (meth) acrylic Latex, trimethylolpropane trimethacrylate, ethylene glycol dimethacrylate, butanediol dimethacrylate, hexaethyl methacrylate, butyl methacrylate or a mixture of two or more thereof, or a urethane-modified acrylate oligomer, epoxy Side acrylate oligo , There may be mentioned ether acrylate oligomers, the dendritic acrylate oligomer, or a mixture of these two or more kinds. In this case, the molecular weight of the oligomer is preferably 1,000 to 10,000.

Specific examples of the monomer or oligomer containing the vinyl group include divinylbenzene, styrene or paramethylstyrene.

Meanwhile, the photocurable coating composition for forming the low refractive index layer may further include a fluorine-based compound including a photoreactive functional group. Accordingly, the binder resin of the low refractive index layer may include a crosslinked polymer between the photopolymerizable compound and the fluorine-based compound including the photoreactive functional group.

The fluorine-based compound including the photoreactive functional group may include or replace one or more photoreactive functional groups, and the photoreactive functional group may participate in the polymerization reaction by irradiation of light, for example, by irradiation of visible or ultraviolet light. It means a functional group. The photoreactive functional group may include various functional groups known to be able to participate in a polymerization reaction by irradiation of light, and specific examples thereof may include (meth) acrylate groups, epoxide groups, vinyl groups, or thiol groups ( Thiol).

The fluorine-based compound including the photoreactive functional group may have a fluorine content of 1% by weight to 25% by weight. If the content of fluorine in the fluorine compound is too small, including the photoreactive functional group, it may be difficult to secure a sufficient stain resistance and physical properties such as alkali resistance of the low refractive index layer. In addition, when the content of fluorine in the fluorine-based compound including the photoreactive functional group is too large, surface properties such as scratch resistance of the low refractive index layer may be reduced.

The fluorine-based compound including the photoreactive functional group may further include silicon or a silicon compound. That is, the fluorine-based compound including the photoreactive functional group may optionally contain a silicon or silicon compound therein.

The fluorine-based compound including the photoreactive functional group may have a weight average molecular weight (weight average molecular weight in terms of polystyrene measured by GPC method) of 2,000 to 200,000. If the weight average molecular weight of the fluorine-based compound including the photoreactive functional group is too small, the low refractive layer obtained from the photocurable coating composition of the embodiment may not have sufficient alkali resistance. In addition, when the weight average molecular weight of the fluorine-based compound including the photoreactive functional group is too large, the low refractive layer obtained from the photocurable coating composition of the embodiment may not have sufficient durability or scratch resistance.

The photocurable coating composition may include 0.1 to 10 parts by weight of the fluorine-based compound including the photoreactive functional group based on 100 parts by weight of the photopolymerizable compound of the monomer or oligomer including the (meth) acrylate or vinyl group. When an excess amount of the fluorine-based compound including the photoreactive functional group is added to the photopolymerizable compound, the coating property of the photocurable coating composition may be lowered or the low refractive layer obtained from the photocurable coating composition may not have sufficient durability or scratch resistance. Can be. In addition, when the amount of the fluorine-based compound including the photoreactive functional group relative to the photopolymerizable compound is too small, the low refractive layer obtained from the photocurable coating composition may not have sufficient alkali resistance.

Meanwhile, the hollow silica particles refer to silica particles having a maximum diameter of less than 200 nm and having empty spaces on the surface and / or inside thereof. The hollow silica particles may have a diameter of 1 to 200 nm, or 10 to 100 nm.

As the hollow silica particles, those whose surfaces are coated with a fluorine compound may be used alone, or may be mixed with the hollow silica particles whose surface is not coated with a fluorine compound. Coating the surface of the hollow silica particles with a fluorine-based compound can lower the surface energy, and thus the hollow silica particles can be more uniformly distributed in the photocurable coating composition, the film obtained from the photocurable coating composition Durability and scratch resistance can be further improved.

In addition, the hollow silica particles may be included in the composition in the form of a colloid dispersed in a predetermined dispersion medium. The colloidal phase including the hollow silica particles may include an organic solvent as a dispersion medium.

Herein, examples of the organic solvent in the dispersion medium include alcohols such as methanol, isopropyl alcohol, ethylene glycol and butanol; Ketones such as methyl ethyl ketone and methyl isobutyl ketone; Aromatic hydrocarbons such as toluene and xylene; Dimethylformamide. Amides such as dimethylacetamide and N-methylpyrrolidone; Esters such as ethyl acetate, butyl acetate and gamma butyrolactone; Ethers such as tetrahydrofuran and 1,4-dioxane; Or mixtures thereof.

The photocurable coating composition may include 10 to 500 parts by weight, or 50 to 400 parts by weight of the hollow silica particles, based on 100 parts by weight of the photopolymerizable compound. When the hollow silica particles are added in an excessive amount, scratch resistance or abrasion resistance of the coating film may decrease due to a decrease in the content of the binder. In addition, when the hollow silica particles are added in a small amount, uniform film formation of the hollow silica particles may not be achieved, and a desired effect may not be properly exhibited due to high reflectance and refractive index.

The photopolymerization initiator may be used without limitation as long as it is a compound known to be used in the photocurable coating composition, and specifically, a benzophenone compound, acetophenone compound, biimidazole compound, triazine compound, oxime compound or Mixtures of two or more thereof can be used.

For 100 parts by weight of the photopolymerizable compound, the photopolymerization initiator may be used in an amount of 1 to 100 parts by weight.

Meanwhile, the photocurable coating composition may further include an organic solvent.

Non-limiting examples of the organic solvent include ketones, alcohols, acetates and ethers, or mixtures of two or more thereof.

Specific examples of such organic solvents include ketones such as methyl ethyl kenone, methyl isobutyl ketone, acetylacetone or isobutyl ketone; Alcohols such as methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, or t-butanol; Acetates such as ethyl acetate, i-propyl acetate, or polyethylene glycol monomethyl ether acetate; Ethers such as tetrahydrofuran or propylene glycol monomethyl ether; Or mixtures of two or more thereof.

The organic solvent may be added at the time of mixing each component included in the photocurable coating composition or may be included in the photocurable coating composition while each component is added in a dispersed or mixed state in the organic solvent.

Meanwhile, the low refractive layer included in the optical film of one embodiment may be obtained by applying the above-mentioned photocurable coating composition on the antiglare layer and drying and photocuring the applied resultant. Specific process conditions of such a low refractive index layer may be in accordance with conditions apparent to those skilled in the art, and are described in detail in the following examples, and thus, further description thereof will be omitted.

Another example of the above-described optical film is a light-transmissive base film;

An antiglare layer comprising a binder containing a (meth) acrylate-based crosslinked polymer and a plurality of light-transmitting fine particles of a sub-micron scale dispersed on the binder; And

A low refractive layer formed on the antiglare layer and comprising a binder resin containing a (co) polymer of a photopolymerizable compound and hollow silica particles dispersed in the binder resin; Including,

When the total average particle diameter of the light-transmitting fine particles is D average, and the light-transmitting fine particles are arranged in descending order from the smallest particle size, the particle size of 25% cumulative particles is D25 and the particle size of 75% cumulative particles When is defined as D75, the (D75-D25) / D average is 0.04 to 0.15,

The absolute value of the difference in refractive index between the light transmitting fine particles and the binder is 0.02 to 0.25,

The total content of the light transmitting fine particles is 1 to 30% by weight of the total content of the antiglare layer,

Reflectance is 0.5% to 2.5%,

It can be an optical film having a 60 ° glossiness deviation value of 3% to 10% and a total haze of 1 to 5%.

As described above, such an optical film can effectively suppress scattering or reflection of external light on the surface of an image display device, in particular, excellent optical properties such as low glossiness and reflectance, and an appropriate level of haze characteristics. Can be represented. Therefore, such an optical film can be very preferably used in various image display devices.

On the other hand, according to another embodiment of the invention, there is provided an image display device including the optical film described above.

An example of such an image display apparatus can be made as follows.

The image display device includes a pair of polarizing plates facing each other; A thin film transistor, a color filter, and a liquid crystal cell sequentially stacked between the pair of polarizing plates; And a liquid crystal display device including a backlight unit, and the optical film of the above-described embodiment may be included on the image display surface side of the liquid crystal display device.

According to the present invention, an optical film exhibiting low glossiness and reflectance and excellent optical properties such as appropriate haze properties, anti-glare properties, and the like can be provided.

Such an optical film is preferably used in various image display devices, and can greatly improve the visibility and the like.

Specific embodiments of the invention are described in more detail in the following examples. However, the following examples are merely to illustrate specific embodiments of the invention, the content of the specific embodiments of the invention is not limited by the following examples.

< Production Example : Antiglare layer  Forming composition and Low refractive layer  Forming Photocurable  Preparation of Coating Composition>

(1) Preparation of composition for antiglare layer forming

The components of Table 1 were uniformly mixed to prepare a composition for forming an antiglare layer. The content of all components used in Table 1 is expressed in parts by weight.

Preparation Example 1 Preparation Example 2 Preparation Example 3 Preparation Example 4 Produce
Example 5 compare
Preparation Example 1 compare
Preparation Example 2 compare
Preparation Example 3 compare
Preparation Example 4 compare
Preparation Example 5 bookbinder UA-306T 4.804 4.426 4.434 5.103 4.804 4.804 4.426 3.426 4.804 8BR-500 8.948 8.223 6.771 6.241 8.948 8.948 4.40 8.223 6.223 TMPTA 22.161 12.313 14.180 22.161 22.161 26.316 22.161 PETA 20.234 11.084 6.241 20.234 15.044 8.948 Organic particulates
(Refractive index) 113BQ
(1.555) 0.999 1.266 0.739 0.849 0.999 0.999 0.202 11.000 0.999 97BQ
(1.525) 1.266 Inorganic particulates
(Refractive index) 9600 A (100 nm)
(1.430) 0.310 0.359 MA-ST (12 nm)
(1.430) 0.200 0.087 0.200 0.220 0.200 0.200 0.03 0.03 0.200 Initiator I184 2.537 2.278 2.337 2.697 2.537 2.536 2.024 2.278 2.024 2.537 Dispersant BYK300 0.269 0.253 0.250 0.280 0.269 0.270 0.506 0.253 0.253 0.269 menstruum IPA 40.058 63.233 61.562 42.550 40.058 40.058 66.522 63.320 62.000 40.058 EtOH 20.024 21.280 20.024 20.024 20.024 Sum 100 100 100 100 100 100 100 100 100 100 Antiglare layer total content ¹⁾
(Part by weight) 37.11 34.24 35.85 33.19 37.11 37.12 30.95 34.12 35.72 37.11 Particulate content / antiglare content (% by weight) 3.231 3.95 3.48 4.30 3.231 3.23 0.75 3.71 30.88 3.231 Refractive index Binder ²⁾ 1.517 1.526 1.521 1.520 1.517 1.517 1.512 1.526 1.526 1.517 Organic particulates
(Average) 1.555 1.555 1.555 1.555 1.555 1.555 1.555 1.525 1.555 1.555 Inorganic particulates (average) 1.430 1.430 1.430 1.430 1.43 1.430 1.430 1.430 1.430 1.430 Refractive index difference
(bookbinder&
Organic particles) 0.038 0.029 0.034 0.035 0.038 0.038 0.043 0.001 0.029 0.038 Refractive index difference
(bookbinder&
Inorganic particles) 0.087 0.096 0.091 0.09 0.087 0.087 0.082 0.096 0.096 0.087

1) The total amount of the antiglare layer is calculated as the total content of the binder and the organic / inorganic fine particles, except for the dispersant, the solvent, and the initiator, which are removed during the formation of the antiglare layer forming composition.

2) The refractive index of the binder is measured after crosslinking (co) polymerization according to the above composition and the production example described later, and the refractive index of the organic / inorganic fine particles is derived as an average value when two or more kinds are used.

1) UA-306T: (Kyoeisha): Hexafunctional acrylate compound formed by reacting two pentaerythritol triacrylates with toluene diisocyanate

2) 8BR-500 (TAISEI FINE CHEMICAL):

A polymer in which a polyacryl main chain is bound to around 40 functional urethane acrylate functional groups.

3) TMPTA: trimethylolpropane triacrylate

4) PETA: Pentaerythritol triacrylate

5) I184 (Irgacure 184): photoinitiator, manufactured by Ciba.

6) BYK 300: PDMS dispersant

7) 113BQ (XX-113BQ, manufactured by Sekisui Plastic): PMMA-PS crosslinked copolymer fine particles having a refractive index of 1.555 and an average particle diameter of 2 μm.

8) 97BQ (XX-97, manufactured by Sekisui Plastic): PMMA-PS crosslinked copolymer fine particles having a refractive index of 1.525 (about 1.53) and an average particle diameter of 2 μm.

9) 9600A: Spherical silica fine particles having a volume average particle diameter of 100 nm and a refractive index of 1.43 (X24-9600A; manufactured by Shinetsu)

10) MA-ST: A dispersion solution in which spherical silica fine particles (product of Nissan Chemical) having a volume average particle diameter of 12 nm and a refractive index of 1.43 are dispersed in methanol at a concentration of 30%.

(2) Preparation of Photocurable Coating Composition for Forming Low Refractive Layer

After mixing the remaining components of Table 2, and diluted with a mixed solution (weight ratio = 1: 1) of MIBK (methyl isobutyl ketone) and IPA, to prepare a photocurable coating composition for forming a low refractive layer. The content of all components used in Table 2 is expressed in parts by weight.

Preparation Example 5 DPHA 1.38 THRULYA 4320 4.56 Irgacure-127 0.55 RS-907 0.51 IPA 46.50 MIBK 46.50 Sum 100

1) DPHA: Dipentaerythritol hexaacrylate, molecular weight 524.51 g / mol, manufactured by Kyoeisha.

2) THRULYA 4320: Hollow silica dispersion, 20 wt% solids in MIBK solvent, product of Catalytic.

3) Irgacure-127: Photoinitiator, manufactured by BASF.

4) RS-907: Fluorine-based compound containing photoreactive functional group, 30 wt% of solids in MIBK solvent, manufactured by DIC Corporation.

<Examples 1-4 and Comparative Examples 1-6: Preparation of Optical Film>

As shown in Table 3 below, the antiglare layer composition prepared in Preparation Examples 1 to 4 or Comparative Preparation Examples 1 to 5 was applied to a PET substrate film having a thickness of 100 μm and a refractive index of 1.6 to 1.7 for 1 minute at 90 ° C. After drying, an anti-glare layer was prepared by irradiating 150 mJ / cm 2 of ultraviolet rays.

In Examples 1 to 4 and Comparative Examples 1 to 6, the low refractive layer on the antiglare layer was formed as follows.

The composition prepared in Preparation Example 5 was applied onto the antiglare layer with Meyer Bar # 3, and dried at 90 ° C. for 1 minute. An optical film was formed by irradiating 180 mJ / cm 2 ultraviolet rays to the dried material under nitrogen purge to form a low refractive layer having a thickness of 100 nm.

Experimental Example: Measurement of Physical Properties of Optical Film

The physical properties of the prepared optical film were measured according to the following method, which is shown together in Table 3 below.

1. Measurement of particle size distribution of translucent (organic / inorganic) fine particles

The particle diameters of the light-transmitting microparticles of organic / inorganic microparticles included in Preparation Examples 1 to 4 and Comparative Preparation Examples 1 to 5 were measured by COULTER PARTICLE SIZE ANALYZER, and were arranged in the order of smallest to largest size. Derived. At this time, the organic fine particles were mixed with a solvent such as ethanol, methanol, and isopropyl alcohol to prepare a dispersion solution and then measured. In the case of the inorganic fine particles supplied in the dispersion state, it was diluted with the same solvent as the dispersion solvent and analyzed.

From the particle size distribution curve, the total average particle diameter of the light-transmitting fine particles is obtained as the D-average, and when the light-transmitting fine particles are arranged in order from the smallest to the largest, the particle size of the fine particles corresponding to 25% cumulative value is D25 and 75% cumulative amount. The particle diameter of the microparticles | fine-particles corresponding to this was calculated | required respectively by D75. From these measured values, the value of (D75-D25) / D average was computed.

2. Refractive Index Measurement

Refractive index of the binder, anti-glare layer, low refractive index layer, etc. included in the optical film was measured in the state of being coated on the wafer using an ellipsometer. More specifically, the refractive index of the binder, the anti-glare layer and the low refractive layer is applied to a 3 cm X 3 cm wafer, each coating, using a spin coater after the coating (coating conditions: 1500rpm, 30 seconds), at 90 ℃ Dry for 2 minutes and 180 mJ / cm ² under nitrogen purge Ultraviolet light was irradiated under the conditions of. This formed each coating layer having a thickness of 100nm.

For this coating layer, a 70 ° incidence angle was applied using a refractive index measuring instrument (model name: M-2000) of J. A. Woollam Co., and linearly polarized light was measured in the wavelength range of 380 nm to 1000 nm. The measured linear light measurement data (ellipsometry data (Ψ, Δ)) was optimized to a MSE of 3 or less by using a Cauchy model of the following general formula 1 using Complete EASE software.

Wherein n (λ) is the refractive index at the lambda wavelength (300 nm to 1800 nm), and A, B, C, are the Kosh parameters.

In addition, the refractive index of the base film and each microparticle used the information provided about a commercial item.

3. Overall / internal / external haze rating

An optical film specimen of 4 cm x 4 cm was prepared and measured three times with a haze meter (HM-150, A light source, Murakamisa) to calculate an average value, which was calculated as the total haze value. In the measurement, the transmittance was measured by JIS K 7361 standard and haze by JIS K 7105 standard. At the time of internal haze measurement, the adhesive film whose total haze was 0 was attached to the coating surface of the optical film to be measured, the surface unevenness was made flat, and internal haze was measured by the same method as the above whole haze.

External haze was computed as the average value of the value which computed the difference of all the haze and the measured value of internal haze.

4. 20 ° / 60 ° glossiness and its deviation value evaluation

20 ° / 60 ° glossiness was measured using micro-TRI-gloss manufactured by BYK Gardner. In the measurement, a black tape (3M) was attached to prevent the light from transmitting to the surface where the coating layer of the base film was not formed, and 20 ° / 60 ° glossiness was measured by varying the incident angle of light at 20 ° / 60 °, respectively. The average value measured 5 times or more was computed as each gloss value.

The deviation value of 60 ° glossiness was calculated by measuring the glossiness ten times by the above method, and then calculating the deviation from the data.

5. Reflectance

Reflectance was measured as average reflectance using the SolidSpec 3700 manufactured by SHIMADZU.

Specifically, a black tape (Vinyl tape 472 Black, manufactured by 3M) is attached so that light does not transmit to the surface where the coating layer is not formed on the optical film, and a sampling interval of 1 mm, time constant 0.1 sec, slit width 20 nm, and medium scanning speed After fixing the measurement conditions, the optical film was measured by irradiating light of a wavelength of 380nm to 780nm by applying the 100T mode.

Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Substrate film PET PET PET PET PET PET PET PET PET PET PET Base Film Refractive Index 1.6-1.7
(Birefringence) 1.6-1.7
(Birefringence) 1.6-1.7
(Birefringence) 1.6-1.7
(Birefringence) 1.6-1.7
(Birefringence) 1.6-1.7
(Birefringence) 1.6-1.7
(Birefringence) 1.6-1.7
(Birefringence) 1.6-1.7
(Birefringence) 1.6-1.7
(Birefringence) 1.6-1.7
(Birefringence) Antiglare Layer Composition Preparation Example 1 Preparation Example 2 Preparation Example 3 Preparation Example 4 Preparation Example 5 Comparative Production Example 1 Comparative Production Example 2 Comparative Production Example 3 Comparative Production Example 4 Preparation Example 1 Comparative Production Example 5 Antiglare Layer Thickness (㎛) 4.5 5.0 4.5 4.0 5.0 4.0 4.5 5.0 4.5 4.5 5.0 D average (㎛) 2.1 1.98 2.1 1.98 2.03 2.02 1.98 2.01 1.98 2.1 2.03 D25 (μm) 1.96 1.84 1.96 1.84 1.96 1.76 1.84 1.85 1.84 1.96 1..96 D75 (μm) 2.15 2.02 2.15 2.02 2.09 2.29 2.02 2.03 2.02 2.15 2.09 (D75-D25) / D average 0.090 0.091 0.090 0.091 0.064 0.262 0.091 0.090 0.091 0.090 0.064 Low refractive layer formation formation formation formation formation formation formation formation formation Unformed formation Low Refractive Layer Thickness (nm) 100 100 100 100 100 100 100 100 100 X 100 Low refractive index 1.41 1.41 1.41 1.41 1.41 1.41 1.41 1.41 1.41 X 1.41 Total haze 3.4 3.3 3.3 3.5 3.5 3.1 0.9 0.6 11.5 3.4 5.4 Internal haze 3.1 2.9 3.1 3.1 3.2 2.8 0.8 0.1 9.2 3.1 5.0 External haze 0.3 0.4 0.3 0.4 0.3 0.3 0.1 0.5 2.3 0.3 0.4 Glossiness (20 degrees) 27.3 28.1 27.6 28.5 28.2 27.8 26.3 27.2 12.4 68.7 23.1 Glossiness (60 degrees) 53.2 52.8 52.6 52.3 53.2 53 51.5 52 48.8 86.6 52.4 60 degree gloss deviation (%) 6.5 6.6 6.5 6.7 6.2 15.1 5.8 8.6 14.3 5.7 7.2 reflectivity(%) 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 3.9 1.5

Referring to Table 3, it was confirmed that the optical film of the example can exhibit excellent optical properties such as low glossiness and reflectance, and an appropriate level of haze properties. On the other hand, Comparative Examples 1 and 4 were found to have a high glossiness deviation value, so that the uniformity of the optical properties was greatly reduced. In addition, in Comparative Example 5, it was confirmed that the glossiness was too high and the reflectance was high to prevent the reflection of external light properly.

In Comparative Examples 2 and 3, since the haze value was too low and the external reflection image was not scattered and visually recognized, it was confirmed that the visibility and image sharpness of the screen were poor. On the contrary, in Comparative Example 6, the internal haze and the total haze value were too high, the optical characteristics were insufficient, and the visibility of the screen was poor.

Claims (13)

Light-transmissive base film;
An antiglare layer comprising a binder containing a (meth) acrylate-based crosslinked polymer, organic microparticles having a micron scale dispersed on the binder, and nanoparticles having a nanoscale inorganic dispersion dispersed on the binder; And
A low refractive layer formed on the antiglare layer and comprising a binder resin containing a (co) polymer of a photopolymerizable compound and hollow silica particles dispersed in the binder resin; Including,
When the total average particle diameter of the organic and inorganic fine particles is D average, the total particle size of the organic and inorganic fine particles is 25% by mass when the particle diameters are arranged in descending order from D25, and 75% by cumulative amount. When the particle size of the corresponding particles is defined as D75, the (D75-D25) / D average is 0.25 or less,
The absolute value of the difference in refractive index between the organic and inorganic fine particles and the binder is 0.04 to 0.15,
The inorganic fine particles are spherical particles having a particle diameter of 10nm to 300nm,
The total content of the organic and inorganic fine particles is 1 to 30% by weight of the total content of the antiglare layer,
An optical film having a 60 ° glossiness deviation value of 3% to 10% and a total haze of 1 to 5%.
The optical film of claim 1, wherein the light-transmitting base film is a cellulose ester base film, a polyester base film, a poly (meth) acrylate base film, or a polycarbonate base film having a thickness of 20 to 500 μm. .
The polymer according to claim 1, wherein the (meth) acrylate-based crosslinked polymer is a polyurethane-based polymer having a (meth) acrylate-based compound having a 3-6 functional monomolecular form and a (meth) acrylate-based functional group having 10 or more functional groups, An optical film comprising a cross-linked (co) polymer of a polyfunctional (meth) acrylate-based compound including a poly (meth) acrylic polymer or a polyester polymer.
The optical film of claim 1, wherein the binder has a refractive index of 1.50 to 1.60.
The optical film of claim 1, wherein the organic fine particles are resin fine particles including a polystyrene resin, a poly (meth) acrylate resin, or a poly (meth) acrylate-co-styrene copolymer resin.
The optical film of claim 1, wherein the organic fine particles are spherical particles having a particle diameter of 1 to 5 μm and have a refractive index of 1.5 to 1.57.
The optical film of claim 1, wherein the inorganic fine particles are metal oxide fine particles including silica, alumina, zirconia, or titania.
The optical film of claim 1, wherein the inorganic fine particles have a refractive index of 1.4 to 1.75.
The optical film of claim 1, wherein the D average is 1.7 μm to 2.3 μm, D25 is 1.5 μm to 2.1 μm, and D75 is 1.9 μm to 2.5 μm.
The optical film of claim 1, wherein the antiglare layer has a thickness of 1 to 10 μm.
The optical film of claim 1, wherein the low refractive layer has a refractive index of 1.3 to 1.5 and a thickness of 1 to 300 nm.
delete  An image display device comprising the optical film of claim 1.